1 files changed, 109 insertions, 0 deletions
diff --git a/testing/mochitest/tests/SimpleTest/paint_listener.js b/testing/mochitest/tests/SimpleTest/paint_listener.js
new file mode 100644
index 0000000000..2fc6ab425a
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/paint_listener.js
@@ -0,0 +1,109 @@
+(function () {
+  var accumulatedRect = null;
+  var onpaint = [];
+  var debug = SpecialPowers.getBoolPref("testing.paint_listener.debug", false);
+  const FlushModes = {
+    FLUSH: 0,
+    NOFLUSH: 1,
+  };
+
+  function paintListener(event) {
+    if (event.target != window) {
+      if (debug) {
+        dump("got MozAfterPaint for wrong window\n");
+      }
+      return;
+    }
+    var clientRect = event.boundingClientRect;
+    var eventRect;
+    if (clientRect) {
+      eventRect = [
+        clientRect.left,
+        clientRect.top,
+        clientRect.right,
+        clientRect.bottom,
+      ];
+    } else {
+      eventRect = [0, 0, 0, 0];
+    }
+    if (debug) {
+      dump("got MozAfterPaint: " + eventRect.join(",") + "\n");
+    }
+    accumulatedRect = accumulatedRect
+      ? [
+          Math.min(accumulatedRect[0], eventRect[0]),
+          Math.min(accumulatedRect[1], eventRect[1]),
+          Math.max(accumulatedRect[2], eventRect[2]),
+          Math.max(accumulatedRect[3], eventRect[3]),
+        ]
+      : eventRect;
+    if (debug) {
+      dump("Dispatching " + onpaint.length + " onpaint listeners\n");
+    }
+    while (onpaint.length) {
+      window.setTimeout(onpaint.pop(), 0);
+    }
+  }
+  window.addEventListener("MozAfterPaint", paintListener);
+
+  function waitForPaints(callback, subdoc, flushMode) {
+    // Wait until paint suppression has ended
+    var utils = SpecialPowers.getDOMWindowUtils(window);
+    if (utils.paintingSuppressed) {
+      if (debug) {
+        dump("waiting for paint suppression to end...\n");
+      }
+      window.setTimeout(function () {
+        waitForPaints(callback, subdoc, flushMode);
+      }, 0);
+      return;
+    }
+
+    // The call to getBoundingClientRect will flush pending layout
+    // notifications. Sometimes, however, this is undesirable since it can mask
+    // bugs where the code under test should be performing the flush.
+    if (flushMode === FlushModes.FLUSH) {
+      document.documentElement.getBoundingClientRect();
+      if (subdoc) {
+        subdoc.documentElement.getBoundingClientRect();
+      }
+    }
+
+    if (utils.isMozAfterPaintPending) {
+      if (debug) {
+        dump("waiting for paint...\n");
+      }
+      onpaint.push(function () {
+        waitForPaints(callback, subdoc, FlushModes.NOFLUSH);
+      });
+      if (utils.isTestControllingRefreshes) {
+        utils.advanceTimeAndRefresh(0);
+      }
+      return;
+    }
+
+    if (debug) {
+      dump("done...\n");
+    }
+    var result = accumulatedRect || [0, 0, 0, 0];
+    accumulatedRect = null;
+    callback.apply(null, result);
+  }
+
+  window.waitForAllPaintsFlushed = function (callback, subdoc) {
+    waitForPaints(callback, subdoc, FlushModes.FLUSH);
+  };
+
+  window.waitForAllPaints = function (callback) {
+    waitForPaints(callback, null, FlushModes.NOFLUSH);
+  };
+
+  window.promiseAllPaintsDone = function (subdoc = null, flush = false) {
+    var flushmode = flush ? FlushModes.FLUSH : FlushModes.NOFLUSH;
+    return new Promise(function (resolve, reject) {
+      // The callback is given the components of the rect, but resolve() can
+      // only be given one arg, so we turn it back into an array.
+      waitForPaints((l, r, t, b) => resolve([l, r, t, b]), subdoc, flushmode);
+    });
+  };
+})();